The present invention relates to a method of manufacturing- filter-tipped cigarettes.
Known filter assembly machines are usually supplied by a cigarette manufacturing machine producing a single continuous cigarette rod travelling axially at substantially constant speed.
As it comes off the manufacturing machine, the continuous cigarette rod encounters a cutting head, usually a rotary type, by which it is usually cut into "double portions", i.e. portions twice as long as that which, when joined to the filter, go to form a normal filter-tipped cigarette. Once cut, the double portions, pushed from the rear by the continuous cigarette rod, continue travelling in said axial direction, and are picked up and transferred successively by a transfer member on to the input element of a filter assembly machine. As described and illustrated, for example, in U.S. Pat. No. 4,577,644, the filter assembly machine normally comprises a series of parael feed rollers, each having a number of peripheral seats for receiving a respective double and feeding it forward transversely in relation to its longitudinal axis.
As they are transferred from the manufacturing machine to the filter assembly machine, the double portions therefore undergo a 90.degree. variation in travelling direction, which transfer is effected by a special transfer member of the type described and illustrated, for example, in U.S. Pat. No. 3,303,926.
As it is fed forward transversely on the filter assembly machine, each double portion is first cut in half, and the two coaxial portions so formed are fed to a parting unit by which they are parted axially- by a sufficient amount to accommodate a double filter, the opposite ends of which are joined to the respective portions to form a double cigarette. The double filter is then cut in half to form two filter-tipped cigarettes.
On known filter assembly machines of the aforementioned type, the parting unit constitutes a critical element in that at least one of the coaxial portions is displaced axially in relation to the other. This invariably involves subjecting each coaxial portion to an axial force which, due to the poor mechanical resistance and high travelling speed of the coaxial portions, cannot be applied directly without damaging them. As a result, known parting units, such as the one described and illustrated in U.S. Pat. No. 4,200,179, are relatively high-cost and so mechanically complex as so seriously impair any possibility-y of further increasing the operating speed of the filter assembly machine.